CIBD: a promising therapy to protect the mucus layer

A western diet significantly modifies the mucosa of the host's colon, in particular the mucus layer. In an animal model, ingestion of fiber and of a strain of Bifidobacterium is thought to help compensate for its effects. This issue warrants close monitoring in the case of Chronic Inflammatory Bowel Disease (CIBD).

The links between dysbiosis and CIBD are constantly strengthened by studies devoted to this research topic. A team of Swedish and Danish scientists wished to conduct a detailed exploration of the impact of our modern diet on the mucus layer of the colon. Mice were fed on a low-fiber, high-fat diet (WSD*) for two months. Compared to the control groups, the mice on a WSD diet displayed a marked deterioration of the mucus layer, which contained lower levels of mucin (Muc2) and was more permeable. This was indicated by the increased presence of the immune protein DMbt1, probably in response to bacterial translocation in the compromised epithelium. With respect to the microbiota, a significant reduction in bacteria from the Bifidobacterium genus was observed from week one, at the same time as a decrease in the thickness of the mucus layer.

Compensating for harmful effects

The team then transplanted the microbiota of each of the two groups–WSD and standard diet–into new populations of mice treated with antibiotics to eliminate their native flora. After six weeks of WSD diet, the mice that had received a transplant of healthy microbiota presented with an intact mucus barrier, that was less permeable, with a better capacity for self-renewal, containing more Bifidobacteria than that of their counterparts that received degraded flora. The healthy microbiota therefore enabled the harmful effects of a poor diet on the mucus layer to be counteracted.

Differentiated protective effects

To test the protective effect of Bifidobacteria, researchers added either a Bifidobacterium longum strain, or inulin (a prebiotic fiber) or both together, to the WSD diet. After a month of supplementation, B. longum indeed helped maintain the development of the mucus layer, without or without inulin. But only inulin had a positive impact on permeability. Other bacterial species, aided by inulin, are therefore likely to be responsible for this protective effect. Although preliminary, these results encourage clarification of the therapeutic potential of some probiotic and prebiotic components in chronic bowel diseases linked to inflammation of the mucosa and deterioration of its mucus layer. At the forefront of these conditions is ulcerative colitis, whose etiology is still unclear while patient quality of life can be substantially improved.